1. Technical Field
The present invention relates to a radiation-curable ink jet composition and an ink jet recording method.
2. Related Art
Ink jet recording methods that use a radiation-curable ink jet composition, an ink jet composition containing a monomer that polymerizes (cures) in response to light, help achieving intended hardness and abrasion resistance of coatings and are suitable for various applications. Such recording methods are thus used in, for example, the production of color filters and printing (recording) on printed circuit boards, plastic cards, vinyl sheets, large-sized signage, and plastic components. In recent years, there is a need for radiation-curable ink jet compositions that give stretchable coatings and thus would allow for printing on curved surfaces and flexible substrates.
Some known radiation-curable ink jet compositions contain a compound having multiple reactive groups to give coatings with sufficient hardness and abrasion resistance.
For example, JP-A-2012-162688 proposes a light-curable ink jet ink composition that contains a bifunctional (meth)acrylate monomer of a particular structure and a urethane (meth)acrylate oligomer having three or more functionalities.
Unfortunately, this light-curable ink jet ink composition is disadvantageous in that increasing the hardness and abrasion resistance of coatings to a sufficient level often affects the stretchability of the coatings. More specifically, when the amount of the bifunctional (meth)acrylate monomer or the urethane (meth)acrylate oligomer having three or more functionalities is large, the coatings tend to be rigid and nonflexible because of an increased number of crosslinks in the coatings. This improves the hardness and abrasion resistance of the coatings, but in some cases can affect stretchability by reducing their room for expansion. Reducing the amounts of these ingredients improves the stretchability of the coatings, but may affect hardness and abrasion resistance.